Hydraulic brake safety unit



April 22, 1941 J. A. WIRTANEN ET AL 2,239,348

HYDRAULIC BRAKE SAFETY UNIT Filed May 5, 1959 v gdg/FATTORNEY.

i put or mammina: circuit in ricree i bythe l Patented Apr. 22, 1941 HYDRAULIC BRAKE SAFETY UNIT John A. Wirtanen Chisholm,

Minn.; said John A.

by order of court, to Elsie anen, Eveleth, deceased, assignor, Wirtanen and Axel M. Wirt- Wirtanen,

' Application May 5, 1939, Serial No. 272,000

l 4 claims. (cl. zoo-s2) This invention relates to safety units for fluid operated.. brakes, the` principal object being to simplify suchV a unit and improve the efficiency thereof, :it being well known that somewhat similar'yui'i'its have been employed with more or less inefficiency.

Another object is to provide such a device having simple means for manual compensation of leakage in the uid circuit.

` Still another object is to provide simple means for repeated signalling in case of trouble'in either pair of or individual vehicle wheel brakes, at each application of the brakes, for a predetermined period of time, and that with a minimum loss of fluid from the system.

Further objects and advantages of the invention will appear as the description of one specic embodiment thereof proceeds.

Referring now to the accompanying drawing, forming part of this application, and wherein like reference characters indicate like parts:

'I'he illustration is that of 'a central vertical sectional view of the unit, showing one embodiment of the invention.

Inasmuch as there has been considerable development in this art, and the action and application of fluid operated brakes for automobiles is well known, there being provided for Ithe operation of such a foot controlled master cylinder and reservoir supply for same, together with the necessary ipe lines leading one to the rear wheels and another to the iront wheels of the automobile, it is deemed superfluous to make additional showing than the view here presented of the auxiliary unit for the purpose of control ci the circuit from the master cylinder to the wheels of the vehicle. l

At i is illustrated the pipe line leading from the master cylinder to the safety signalling cylindei 2, embodying the present invention. From adjacent either endof this cylinder 2 there are .pipe lines l and I leading respectively to the front and rear wheel brakes ot the vehicle.

The cylinder 2 is of ordinary construction except that on one side thereof there is a slight enlargement] in which enlargement is provided the by-pass channel 8 communicating with both ends of the cylinder as well as the middle thereof, and which communicating connections are controlied as by suitable thumb or other screws indicated at l. At either end of this cylinder and substantially axially thereof is installed a suitable insulated electric terminal Il which forms numeral I.

Within the cylinder 2 are installed two spaced floating pistons Il, they being held in predetermined spaced relation substantially as shown by the expansive helical spring I2 which of course is provided at either end thereof with suitable impinging gaskets indicated at I3 to insure against leakage of fluid during the action of the piston. Upon the opposite side of each piston II and installed within the cylinder 2 is a similar expansive helical spring I4, thetension of which springs is such asto maintain the pistons normally in proper spaced relation, as The fluid supply I from the master cylinder to the center of the cylinder 2 discharges into the chamber I5 intermediate-of the pistons II, and in which chamber -the spring I2 is installed, while the uid connections 3 and 4 from the brakes to be controlled are shown as communicating with the chambers within the cylinder 2 of the unit upon the opposite sides of the pistons, said chambers being indicated at I6.v

It is of course understood that before operation of the device the system must be provided with the necessary fluid for such operation, and to accomplish which both ends of the cylinder 2 must be adequately filled with the fluid. For this purpose the ports controlled by the screws 9 must be regulated to provide open communication to both ends as well as the middle of the cylinder through the by-pass 8. Thus when uid is admitted from the connection I into the chamber I5 filling the same, itmay pass through the bypass l and ports at either ends thereof into the chambers It filling the same and the lines 3 and 4 to the brake mechanism on the Wheels of the vehicle. Then on closing the ports controlled yby the screws 9 the device is in readiness for operation as a safety signal means, in that when iiuid is forced into the chamber I5 intermediate of the pistons II. as for example when the vehicle brake pedal is depressed, the pistons will be forced apart, and the liquid in the chambers I8 caused to function normally in the operation of the braking mechanism. from any cause, or abnormal wear of the brake shoes, occur, ing more than a normal predetermined distance. it will bring into action the signal means, hereinafter described.

This signal means comprises an auxiliary cylinder Il screw threadedly mounted within the outer face of each piston II. Each auxiliary cylinder I1 has installed therein a reciprocal piston Il carried uponl y illustrated. r

However, should a leakso astoresultineitherpistonmov-l the inner end ofI the terminal stem Il. which protrudes through the end oi each cylinder I1 and at the opposite end of the piston I8 within each cylinder is an expansive helical spring 20 for holding the terminal stem I9 in its outermost position. Suitable holes 2| are provided through the wall of each cylinder l1 to permit of free circulation of Oil therein. Now it is to be understood that the cylinder 2 is suitably grounded for example as indicated at 22 for completion of the electric circuit when the signalling operation occurs, and when either of the terminal stems I9 engage their respective opposed terminals l0, the circuit will be closed to its respective lamp and thus cause the desired signal. However it is to be noted that ample space is allowed for normal action of each piston il within the cylinder for many repeated applications of the brake when in normal condition, or the gradual increasing in distance of action through normal wear until such time as the terminal stem i9 engages the opposite terminal in its circuit. Even after the stem i9 engages its respective opposite terminal when the brakes are applied there is provided means for repeated signalling at each application of the brakes for a predetermined number of times before all braking action would cease; this being due obviously to the yieldability of the terminal stem within its auxiliary cylinder and which is controlled by the spring 20. Thus it is deemed wefhave provided not only a practical saiety signal'means for hydraulic brake systems, but a very simple and eilicient structure that provides for repeated warning signals to the operator of the vehicle that the brake system needs attention, and that before the brake system completely fails.

From the foregoing it is apparent'that a single cylinder installation of this type will adequately function for the control of the front and rear brakes in pairs, that is to say for example that both front brake mechanisms are controlled by the connection 3, and both rear brakes by the connection 4. However in some installations it uld lled cylinder, an electric circuit terminal in either end of said cylinder, a pair of spaced pistons within said cylinder, means intermediate 'of and holding said pistons in spaced relation,

of said cylinder falls below a predetermined' amount.

2. A circuit closer comprising an elongated iiuid lled cylinder, a pair of spaced liiuid actuated pistons within said cylinder, means for the access of uid to said cylinder intermediate may be desirable tov have the signal indicate' which specic wheel brake was faulty, and in such cases a double safety cylinder could be provided, and wherein there would be two connections 3, one to each front wheel brake, and two connections 4, one to each rear wheel brake, and thus provide an accurate check on the operation of the. brakes of each wheel; the broad concept of a signal to indicate faulty operation of each wheel brake, however, being old in the art.

Having thus described our invention, what we claim and desire to secure by Letters Patent. is: 1. A circuit closer comprising, an elongated of and to move said pistons, a spring actuated oating piston carried by either iluid actuated piston, an independently yieldable circuit contact element, associated with each floating piston, and cooperative contact elements at either end of said cylinder, said contact elements being held in normally spaced relation by the iiuid within said cylinder, and whereby when iluid within said cylinder falls below a predetermined volume said elements may contact each other and close a. circuit.

3. A circuit closer comprising an elongated iiuid lled cylinder, having a central fluid inlet, reciprocable pistons within vsaid cylinder, each operable toward an end of said cylinder by fluid entering said central inlet, a yieldable contact element carried by the outer surface of each piston, .and a stationary contact element carried by each end of said cylinder, the iiuid normally within said cylinder preventing said elements from contacting each other, and whereby when fluid within said cylinder falls below a predetermined volume, said elements may contact each other and close a circuit.

4. A circuit closer comprising an elongated 4-iiuid iilled cylinder having a central fluid inlet,

a terminal of an electric circuit at either end of said cylinder, opposed pistons operable within said cylinder, one upon either side of said inlet and adapted to be actuated by uid entering the cylinder through said inlet, and a yieldable contact element carried by each piston, for cooperative engagement with the terminal of an electric circuit in each end of 'said cylinder when the iluid within either end of said cylinder falls below a predetermined volume.

JOHN A. WIRTANEN. AXEL M. WIRTANEN. 

